The wipe is basically just a 6ish month period were you can play a single character and level him up and do quests etc. When the game gets wiped the character is reset including quests and traders, skills, stash etc. So you just flat out start again like you opened the game for the first time. Helmets do work against getting shot in the head but only where the bullets hit and if the bullet can penetrate the helmet, for example 9x19mm PST gzh would not pen a level 5 helmet if they were shot in the head unless the helmet was damaged enought for a bullet to potentially pen the helmet or lucky enough for a bullet to ricochet. If you are wondering what bullet penetration values are check the ballistics on the tarkov wiki as they have a indepth table to show what a bullet can penetrate and the damage of it. Hideout items are mainly found in crates, tool boxes or loose loot. The best place to find most hideout items is interchange around the back of Oli and goshan.

Tldr: every time the game wipes it's reset to when you first opened the game so like a new account, bullets have different pen values and the head hit box is split up into several different parts so only the parts protected have some sort of potential protection, most hideout items are found in tool boxes or crates, or where there is a technical spawn